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Mike is a middle school student. He is 16 years old. He had a bad cold last night. He felt bad and couldn't eat anything. So he went to see a doctor. The doctor gave him a bottle of medicine. But he doesn't know when to take the medicine. Can you tell me what the doctor means? These are the instructions (用法说明):

You should shake (摇晃）it before you take. Take it three times a day after meals. Dose (剂量) Age: over 15    2 teaspoonfuls 8-15       1 teaspoonful 5-7        1/2 teaspoonful Children under 5 years old can't take this medicine. Please put it in a cool place. Take it before June 1st, 2014.